Rotary drilling methods employing a drill bit and drill stems have long been used to drill wellbores in subterranean formations. Drilling fluids or muds are commonly circulated in the well during such drilling to cool and lubricate the drilling apparatus, lift drilling cuttings out of the wellbore, and counterbalance the subterranean formation pressure encountered. The recirculation of the drilling mud requires the fast and efficient removal of the drilling cuttings and other entrained solids from the drilling mud prior to reuse. Shaker separators are commonly used to remove the bulk solids from the drilling mud.
A shaker separator consists of an elongated, box-like, rigid bed and a screen attached to, and extending across, the bed. The bed is vibrated as the material to be separated is introduced to the screen which moves the relatively large size material along the screen and off the end of the bed. The liquid and/or relatively small sized material is passed into a pan. The bed can be vibrated by pneumatic, hydraulic, or rotary vibrators, in a conventional manner.
Various solids are brought up from the wellbore with the mud, including drill cuttings, clay, and debris. Sometimes clay that is directed into the shaker separator with the drilling fluid is sticky and heavy. Such solids risk causing screen breakage because they stick to the screen and are not transported to the discharge end of the shaker in an efficient manner. In such cases, it is desirable to lower the discharge end of the shaker bed to assist in the removal of the sticky solids from the screen.
At other times, coarse solids are easily conveyed along the top of the screen by the vibratory motion of the shaker. In order to preserve the drilling mud and increase the volume flow rate of the mud being directed into the separator, it is desirable to raise the discharge end of the shaker bed. When the discharge end is raised, the mud flow rate may be maximized while mud loss over the screen is minimized.
Some shaker separators have been built with systems to elevate the discharge end of the shaker bed. Many of these systems have employed manual operation techniques, such as hand wheels or jacks, to raise and lower the end of the bed. Other systems have included hydraulic lifts that are independently actuated, often requiring time and finesse by the operator to laterally level the discharge end of the shaker bed. Further, these systems have also included solenoids, which may be undesirable in the hazardous locations in which shaker separators are often used, particularly when separating drill cuttings from drilling mud. Thus, there is a need for a system to raise the discharge end of the shaker bed quickly and safely while keeping it level from side to side.